Intelligence statements generally have a shelf life; confidence in them often decays as the statement grows older for a number of reasons. Depending on how long ago the statement was made, by whom it was said, and the content of the statement, analysts might treat intelligence differently, or discount it completely. For example, a person's description might be wholly accurate for only a few hours, as the subject might change appearance characteristics soon after the statement was made. Some types of characteristics, such as height and weight, can take longer to change, while other characteristics might be permanent. Financial structures and assets have a shelf life based on the asset type, influence from external factors and acceptable trading guidelines. Statements that relate to a financial asset may need to be adjusted based on several of these factors and in some cases discounted.